Pardon me asking but why must the CPL be on the outside of the filters? If I use a 72mm CPL on the 18-200 VR followed by at most 1 or 2 GNDs/NDs, will it cause vignetting?
Wanted to get started with a Lee filter system but if I can only afford two filters, which two will be recommended? The filters will be used only with the 18-200 (my only lens ;p)
Becoz after you mount the holder onto your lens, you cant turn your CPL. So you have to get the Lee CPL & ring adaptor to mount on the outside so you can turn. 18mm on 1.5x crop may not cause serious vignetting with up to 4 filters. I'm using 16-35 on full frame and at the widest end, i can only use up to 2 filters to prevent vignetting.
If you intend to get 2 filters, I would suggest a 2-3 stop GND & 3 stop ND. For the latter, its better to get the 3 NDs pack ( 1, 2 & 3 stop) @ $99 only as it cost about $40 each if you purchase them separately. Afterall, i've slightly regretted buying the set as I dun find any difference with my existing CPL or maybe I'm still trying to figure out how to use it.